The invention pertains to electric motor drive units of the type wherein a worm wheel housing constitutes an end cap of an electric motor casing.
The electric motor drive units commonly employed within automobile doors and side panels to electrically operate the window regulators must be of a concise configuration in order to permit installation in limited space. Additionally, such drive units must be capable of producing relatively high torque, yet must be able to withstand reactive forces tending to stall the motor at the end of window travel.
In order to achieve the desired torque requirements worm wheel and worm drives are often employed in electrically powered vehicle window regulator devices. However, difficulties have been encountered in producing such units economically which are capable of long lasting dependable operation. Considerable difficulty has been encountered in maintaining the alignment of the worm and worm wheel wherein the worm constituted an extension of the motor armature shaft, and such arrangements also require expensive machining techniques as well as complicate the assembly of the unit. Further, in installations where a worm shaft and armature must be aligned difficulty is often encountered in maintaining the required alignment tolerances after installation and use.
As vehicle regulator drive units are manufactured in large quantities it is necessary that the cost of manufacture be minimized, and yet the complexity of the device, assembly and alignment problems, and the hard use that window regulators are subjected to, has resulted in a relatively high priced item capable of achieving a broader market if the cost thereof were reduced.